Philip Hensher: Rules of behaviour that were once understood are now vexing us all

One of the familiar errors in literary dialogue lies, in my view, in the use of the word "Dear" as a vocative.

Whenever I read in a recent novel a middle-aged couple saying "What do you want for lunch, dear?", I always think that the novelist hasn't actually listened to people talking for years, or perhaps ever. English has a general problem with natural-sounding vocatives, but "dear" went out in normal speech about the time when women wore hats before stepping out of doors, and everyone announced their number on picking up the phone.

So it has become an item in a kind of discourse parallel to reality, rather than continuous with it. To use "dear" as a vocative announces one of several things. One, that you are quoting something. Two, that you are making a linguistic gesture which could really best be described as camp, or ironic. (One Hoxton hipster to another: "Pop your pinny on, dear, and let's have a nice cup of tea.") Three, that you are writing quite a bad novel, or BBC2 sitcom.

When the Prime Minister said "Calm down, dear" to Angela Eagle in the middle of Prime Minister's Questions this week, he exposed a number of painful gaps in our knowledge of how to behave today. Do we even know any more what the proper way to speak to each other is, in any given setting?

The use of the phrase "Calm down, dear" seemed inappropriate in the setting, from that particular person, in two quite different ways. They each suggested a certain social anxiety. In a week when we were asked to consider our social structure in the theatrical setting of a royal wedding, those social anxieties might bear thinking about. On the one hand, the Labour Party rose up in indignation that someone might say "dear" to a woman – sexist and misogynist, it was said. On the other hand, Angela Eagle said only that she had "been patronised by better people than the Prime Minister", suggesting that she was used to it. But had the Labour Party been listening to the overtones in the Prime Minister's remark? Does he, seriously, ever say "dear" to a woman with the serious intention of patronising her? Or does his remark fall into my second category, of a camp linguistic gesture? There may be elderly men in Mr Cameron's party who say "dear" seriously to waitresses still – come to think of it, Mrs Thatcher used to say "Thatcher, dear" to me when I had the job of ticking her off on division sheets, which probably wasn't misogynist. But I doubt a man of David Cameron's age and class ever says "dear" without ironic intent.

Whether or not a prime minister should be making these camp ironic remarks while responding to questions in the House of Commons is another question. Another school of thought found a second, perpendicular fracture between role and speech in the Prime Minister's words. Should a prime minister be defending his august policy by explicitly quoting the slogan of an irritating insurance advert starring Mr Michael Winner? Is this the sort of thing that people are allowed to do, nowadays, if they are the prime minister answering serious questions?

Nobody really knows the answers to these questions any longer. One set of new principles is outraged on the one side, the one where we don't use quondam terms of affection for women we aren't that close to. On the other, some old principles of decorum and dignity have not quite disappeared, and are just as willing to be offended by aspects of modernity.

These questions have been described as trivial in the extreme, and not worth the acres of newsprint and discussion spent talking over them. But at a time when we are defining our modes of behaviour, we are always going to engage with great energy over the smallest issues. The match of propriety to role and setting is never decided over large issues of principle; they are decided, inch by inch, over words of address and presentation. Subsequently, people wonder why such tiny issues became so significant, while remaining blind to the tininess of their own issues.

Often, too, these issues are decided through an acting-out of assigned roles, or a refusal of those roles. David Kynaston, the historian of post-war Britain, has a nice vignette of a public schoolboy in 1945 calling out to a railway porter "My man", and being told: "No, all that is over now." That refusal of role and hierarchy was being played out, in one ironic and playful way, by the Prime Minister pretending to call Angela Eagle "dear".

In another, potentially more deadly serious, it was played out at one of those great theatrical statements of idealised society, the marriage of the Duke and Duchess of Cambridge. This, we are always told, is what the British do best. And indeed it is. A surprising amount of the pre-wedding discussion – in Britain, at least; it didn't much interest foreign commentators – focused on what guests were going to wear. Would the Prime Minister wear a lounge suit? Would his wife wear a hat? What – this became weirdly prominent – were Mr and Mrs David Beckham going to wear, since that was surely the new measure, not just of style, but of propriety?

In the end, Mr Cameron wore morning dress; Mrs Cameron wore no hat, but jewels in her hair; Mr Beckham wore his OBE with great conspicuousness on his tailcoat, though I could not tell you whether that is correct or not; and Mrs Beckham wore a kind of squiggle in front of her face which could only belong to Fashion.

Now, all of this may seem desperately trivial, but it indicates an ongoing anxiety about propriety, role and performance in the highest settings which suggests that we are just not very sure how to behave any more. And that is even in the most formal settings anybody is likely to encounter. All those little informalising gestures which have entered into society in the past 30 years have had a stressful effect on a large number of people. Calling strangers, colleagues and bosses by their first names; kissing on departure; expecting to stay in contact by telephone at all hours of the day and most of the night; dress-down Fridays and compulsory workplace banter – all these are examples of a society in stressful flux. I don't say they are all regrettable changes; we live in a much friendlier, more relaxed society than 30 years ago. But before rules of engagement and behaviour are properly formalised, we are going to go through a longish period when nobody is quite sure how they are supposed to behave.

What we can expect to see, at every level, are exactly those curious dramas, resting on single words or gestures, that we saw at Prime Minister's Questions this week. An outdated word is used flirtatiously, without serious intent, trying it out; a posture of insult is adopted; gestures of outrage by onlookers, discussion of propriety, and nothing much concluded, or so it seems. In short, while we are still deciding how it is that we are going to deal with each other, a certain amount of forbearance, a degree of a sense of humour might be called for.